Pressure vessel having frangible opening means



July 28, 1970 BOCK ET AL 3,521,786

PRESSURE VESSEL HAVING FRANGIBLE OPENING MEANS Filed Sept. 10, 1968 2Sheets-Sheet i FIG. I FIG-3 /4 34% I /flfl AZ 4 j] jg /W6 35 & w w Xv r45 a? XX :1 4 4 United States Patent 3,521,786 PRESSURE VESSEL HAVINGFRANGIBLE OPENING MEANS Herbert G. Bock, Farmington, and Walter J.Szerejko, Newington, Conn., assignors to Chandler Evans Inc., WestHartford, Conn., a corporation of Delaware Filed Sept. 10, 1968, Ser.No. 758,904 Int. Cl. B65d 17/00 US. Cl. 22027 4 Claims ABSTRACT OF THEDISCLOSURE A metal high pressure gas storage vessel has a threaded neckadapted to engage a threaded cap such that both cap and neck sealinglybear against an interposed seal element. The seal and cap are looselyassembled with the empty bottle and placed in a fluid tight fillingfixture whereupon highly pressurized gas is introduced to the fixture,causing the bottle to fill by leakage between the loosely engagedthreads. Then the cap is tightened and the fixture is vented prior toremoval of the filled bottle. To lock the cap against rotation, the capis locally upset into grooves in the neck after the acceptability of thecharge has been verified.

BACKGROUND OF THE INVENTION Missile flight control systems havingaerodynamic fins positioned by cold gas powered actuators generallyinclude a pressure vessel to supply pressurized gas. Conservation ofvehicle weight to increase payload capacity makes high pressure heliuman attract gas source for actuator power. An efficient and reliablesealing technique is necessary to insure that adequate pressure will beretained in the vessel after storage of long duration under adverseenvironmental conditions. Reliability can be enhanced by utilizing avessel having a single unvalved opening therein. Optimum sealing can beobtained using a threaded cap configuration to which a specific optimumtorque is applied. The optimum torque requirement of the threaded capconfiguration would be compromised if traditionally accepted threadedvessel closure means are used which require that the vessel and closureoccupy one of a number of discrete angular positions with respect toeach other to permit an alignment of means intended to interlock saidvessel and closure against inadvertent rotation. Storage duration andconditions prohibit the use of threaded joint sealants which may besubject to degradation or the use of check valves subject to open undervibration or shock loads. Furthermore, the use of a thread sealant wouldinterfere with the pressure vessel filling process.

SUMMARY Reliable sealing of high pressure helium requires a bettertechnique than the conventional check valve type of fill valve used onmost small pressure vessels. The efiicient sealing of high pressuregaseous containers to prevent leakage is directly affected by the degreeof uniform pressure that can be exerted on the sealing member. One ofthe most efficient high pressure sealing methods involves deforming asoft metal strip between two hard metal surfaces. The uniformity withwhich the load is distributed over the entire area of the soft metalstrip to be deformed directly affects the efficient sealing of thisparticular type of sealing device.

The present invention provides a method of filling a vessel having athreaded closure through loosely engaged threads and of permanentlyfastening one of the hard sealing elements to the other once theappropriate uniformly distributed load has been applied to thedeformable sealing element. The permanent fastening means 3,521,786Patented July 28, 1970 comprises an annular projection extending fromthe open end of the internally threaded hardened element such that thisannular projection or ring circumscribes the externally threadedhardened element. This annulus or ring so encompasses the externallythreaded hardened element that once the desired torque has been appliedto the internally threaded element to permit the uniformly distributedload to be applied to the soft deformable element, two localized areasof the annular projection or ring can be upset or deformed into twolongitudinal grooves or slots cut into the periphery of the externallythreaded hardened element. This localized upsetting action permanentlyfastens the two threadable engaged hardened elements to each other.

Some of the objects of this invention are:

To provide a high pressure storage vessel having highly reliable sealingcapabilities by virtue of having only a single opening therein;

To provide a threaded closure for the single opening of a pressurevessel and means to lock the closure and vessel in an infinite number ofpositions;

To provide a pressure vessel closure adapted to permit the pressurevessel to engage a fluid distribution system;

To provide apparatus whereby a pressure vessel may be filled;

To provide a method for filling a pressure vessel and ascertaining thatthe pressure vessel has in fact been filled to the proper charge.

It is a further object of this invention to provide a puncturablesealing diaphragm and a rotatable threaded sleeve each urging saiddiaphragm into sealing engagement with a sealing surface of a containerwhile restraining said diaphragm against rotation relative to saidsealing surface and simultaneously providing for staking said sleeve atany desired sealing torque.

Further objects will be apparent to those versed in the art afterexamination of the specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial side elevationview of an assembled pressure vessel and cap utilizing the presentinvention.

FIG. 2 is a side elevation view of a pressure vessel filling apparatusaccording to the instant invention.

FIG. 3 is a side elevation view of a preferred capped pressure vesselutilizing the instant invention threadably engaged with a fluiddistribution system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a pressurevessel 10 has an externally threaded hollow neck section 12 with a firstannular beveled sealing surface 14 and at least one longitudinal localrecess 16 disposed on the periphery of said neck section 12. Adiaphragm, shown generally at 18, has a cylindrical body 20 with oneclosed end 22 and an open end having an outwardly projecting terminalflange 24 thereon, said flange 24 defining a second annular beveledsealing surface 26 having a bevel angle 28, surface 26 beingsubstantially the mate to sealing surface .14. The bevel angle 28 ofsurfaces 14 and 26 is preferably 37 with respect to the vessellongitudinal axis. A metal to metal seal is preferred to form a reliableseal under adverse environmentally storage conditions of high stress,humidity, temperature, fungus, dirt, shock and vibration. If a largehardness differential exists between surfaces 26 and 14, an interposedsealing element 30 is not required. However, in the preferredembodiment, where surfaces 26 and 14 are of similarly hard steel, afrustoconical sealing element 30, preferably of tin plated copper whichwill readily flow under high pressure to fill any minor imperfections insealing surfaces 26 and 14,

is inserted between said sealing surfaces. A diaphragm retaining sleeve,shown generally at 32, has internal threads 34 which engage externalthreads 33 on neck section 12. Inwardly projecting flange 36 integralwith sleeve 32 urges diaphragm terminal flange 24 towards neck section12 as the engagement between sleeve 32 and neck 12 is increased, thusloading surfaces 14 and 26 against each other or against sealing element30 if an interposed sealing element is utilized. A slight clearanceprovided between flange 36 of sleeve 32 and cylindrical body 20 causessealing surfaces 14 and 26 to mate properly despite minor misalignmentof the sealing surfaces with the respective threaded members. Sleeve 32and diaphragm 18 form a cap somewhat analogous to a conventionalthreaded bottle cap. Once the desired axial sealing force has beenattained as indicated by measurement of torque required to advance theengagement of sleeve 32, an annular lip 38 integral with sleeve 32 isinelastically deformed into recess 16 to fix the relative positions ofsaid vessel 10, diaphragm 18 and sleeve 32 so as to preserve andmaintain the integrity of the seal.

Sleeve 32 has external threads 40 thereon which as shown in detail inFIGS. 2 and 3 are useful both for filling the vessel and for achievingsealed installation of the vessel in a pressure distribution systemhaving therein ram means to puncture closed end 22 of diaphragm 18. Aportion of the cylindrical body 20 of diaphragm 18 is elongated andcarefully finished to sealingly mate with an O-ring seal 102 housed insaid pressure distribution system shown in FIG. 3.

Referring to FIG. 2, a fill fixture, shown generally at 50, comprises aflanged base 52 and a flanged cover 54 held together by a hinged splitring 56 adapted to be closed by a handle (not shown) having a cammingaction whereby a large lever ratio is applied to axially urge togetherflanges and 53 of base 52 and cover 54 respectively. Bore 58 in base 52is adapted to receive vessel 10 loosely therein, support being given tosaid vessel by a contoured support sleeve 60 positioned in the base ofbore 58 such that the end of vessel 10 will not bottom in bore 58. Alarger threaded bore 62 in base 52 is adapted to threadably receive acylindrical loading collar 64 having an inwardly extending flange 65 andconically tapered interior surface 66. Flange 65 bears against acontoured thrust ring 68 which loads vessel 10 against support sleeve 60and tapered centering ring 70 through conical surface 66. Loading collar64 is torqued to a value in excess of the torque to be applied later tothe vessel cap so that when the latter torque is applied the vessel willnot turn within the fixture. A smooth bore 72, still larger thanthreaded bore 62 is adapted to sealingly receive an O-ring seal 71positioned in cylindrical extension member 74 integrally connected tocover 54. It is to be noted that before cover 54 is secured in place, asplit nut 76 having internal threads 78 is affixed to vessel sleeve 32such that threads 78 engage external threads 40 on sleeve 32 and suchthat an internal shoulder 80 on nut 76 bears against flange 36 on sleeve32. A tapered ring 82 is driven onto split nut 76- with care being takennot to disturb a spring clip 84 placed on the elongated body 20 ofdiaphragm 18 to grasp said diaphragm and bear against flange 36 ofsleeve 32. Clip 84 prevents pressure in the fill fixture from forcingdiaphragm 18 into fluid tight engagement with sealing element 30 (shownin FIG. 1) while the cap is slightly backed off to permit gas to entervessel 10. Nut 76 has therein a rectangular slot 83 adapted to receivedriver bit 86 integral with shaft 88 mounted for rotation in bushing 90in cover 54 and sealingly engaged by O-ring seal 91 in said cover. Shaft88 has a flange 92 thereon and a low friction thrust washer 94 isinterposed between said flange and said cover to minimize the torsionalfriction component caused by the gas force tending to blow shaft 88 outof the cover.

With cover 54 sealingly engaging and locked to base 52, gas is suppliedfor a few seconds to bore 116 via passageway 110' and gas fill source112 while a fixture vent valve 114, well known in the art, is held opento purge the fixture of air. When the purging operation is complete, thevent valve 114 is shut and the fixture brought to a pressure somewhatbelow the desired charge pressure whereupon the temperature within thefixture is recorded and the fixture is pressure filled to the final fillbased upon a pressure calculated on the basis of the pressure desiredwhen the fixture has cooled to room temperature. The final charging flowis permitted to fill the fixture and torque is applied to shaft 88 torotate split nut 76 thereby causing sleeve 32 to rotate split nut 76thereby causing sleeve 32 to rotate therewith and, as shown in FIG. 1,drive diaphragm 18 against sealing element 30 and neck 12 until thedesired torque has been provided for optimum sealing. Thereafter thefixture is vented and the cover removed. Tapered ring 82 is removed andthe split nut 76 taken off. Loading collar 64 is unthreaded from base52, items 68 and 70 are removed, and the vessel is removed and weighedcarefully to ascertain that the weight increase from a previouslyrecorded empty weight indicates the desired weight of gas. A massspectrometer is utilized to ensure that the leakage rate is consonantwith the specified storage duration; if the leakage rate issatisfactory, lip 38 is crimped into recess 16 to lock the cap in place,as shown in FIG. 1.

Referring to FIG. 3, vessel 10 by means of external threads 40threadably engages a distribution manifold with O-ring seal 102 engagingelongated body 20 on diaphragm 18. When an electrical command signal isdelivered to an explosively actuated cutter valve 104, a ram 106 thereinpunctures end 22 of diaphragm 18 permitting vessel 10 to supplypressurized gas to passageways within manifold 100 leading to variousfin actuating mechanisms.

By way of illustration, an embodiment of the instant invention is shownthat limits leakage such that an initial nominal charge of ten cubicinches of Grade A helium at 6800 p.s.i. will be at no less than 6680p.s.i. after a five year storage period. The material used for sleeve32, diaphragm 18 and neck section 12, shown in FIG. 1, is AMS 6370having a nominal C Scale Rockwell hardness of twenty-nine. The matedfrustoconical sealing area between surfaces 14 and 26, shown in FIG. 1,has an approximate ID. of .297", an OD. of .435", and a bevel angle of37 with respect to the vessel longitudinal axis. The thread engagementbetween sleeve 32 and the neck section 12 is .562-18 UNF-ZA and 2Bmodified by tip relief to insure a clearance through which vesselfilling can take place prior to sealing the vessel. The torque appliedto sleeve 32 to insure an optimum seal under these conditions (using acopper sealing element 30 with .0003" tin plate per MIL-T-l0727) isnominally 315 inch pounds. The deformable annular lip 38 has a radialthickness of approximately .020" and two longitudinal diametricallyopposed grooves 16 are approximately 0.100" wide and .030" deep.Approximately 10 grams of helium are added and leakage must not exceed9.2x l0 atms. cc./ sec. as determined by mass spectrometer analysis.

It will be apparent to those skilled in the art that various changes andmodifications may be made in the construction and arrangements of thevarious elements; accordingly, the description and drawings have beenset out to illustrate rather than limit the inventive concept.

What we claim is:

1. In combination in a pressure vessel having a single variableaperture,

a container having a hollow neck section defining a first annularbeveled sealing surface and at least one longitudinal local recessdisposed on the periphery of said neck section,

a diaphragm having one closed end, and opposite said closed end an openend having an outwardly project ing terminal flange thereon, said flangedefining a second annular beveled sealing surface substantially matingsaid first beveled sealing surface,

a diaphragm retaining sleeve adapted to engage said neck section, saidretaining sleeve having thereon an inwardly projecting flange and anannular lip, whereby engagement between said retaining sleeve and saidneck section causes said inwardly projecting flange to urge saiddiaphragm towards said neck section such that at any desired degree ofsealing engagement said annular lip is inelastically deformed into atleast one of said longitudinal local recesses to thereby fixedly securethe relative position of said neck section, said diaphragm and saidretaining sleeve.

2. A pressure vessel assembly, as claimed in claim 1, including asealing element more yieldable than said first and said second beveledsealing surfaces and disposed between said first and second sealingsurfaces.

3. A pressure vessel assembly, as claimed in claim 1, including incombination with said pressure vessel assembly a manifold sealinglyengaged to said pressure vessel 6 assembly and having therein means topuncture said diaphragm and initiate fluid flow from said pressurevessel. 4. A pressure vessel assembly, as described in claim 2, whereinsaid diaphragm detaining sleeve has external threads disposed thereon,and said diaphragm has an elongated cylindrical surface thereon adaptedto engage yieldable sealing means such that the entire assembly may becaused to sealingly engage a manifold having thereon means to puncturesaid diaphragm to thereby initiate fluid fiow from said pressure vessel.

References Cited UNITED STATES PATENTS GEORGE T. HALL, Primary ExaminerUS. Cl. XJR. 220 3; 22989 1% UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 31;,521 786 Dated July 28, 1970 lnventorts)Herbert E Book and Walter J Szereiko It is certified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected as shown below:

IN THE SPECIFICATION:

Column 1, line 33, change "attract" to attractive Column 4, lines 13 and14, after "rotate, delete split nut 76 thereby causing sleeve 32 torotate IN THE CLAIMS:

Claim 4, line 2 (Column 6, line 4) ,change "detaining" to retainingSigned and sealed this 21st day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'ISCHALK Attescing Officer Commissionerof Patents

